Agreed. Page appearing in Category:Tag descriptions with status “deprecated” definitely does not mean it is actually deprecated by the community.
The page appearing in that category is however quite a good reason to check:
- content of that wiki edit itself
- metadata of that wiki edit (wiki comment)
- page https://wiki.openstreetmap.org/wiki/Deprecated_features#Deprecated_features
for details of the reasons for deprecation (or lack thereof), and doing appropriate actions depending on the results (like discussing the issue with the user, discussing with wider community on talk page / tagging ML / community forum, reverting wiki to the previous status quo until the consensus is reached, or taking further actions if needed)
I’d only wish if MediaWiki allowed one to use follow new pages appearing in the category via RSS, as it would make for much easier following of it. Or some way to find tags which are listed in that Category, but are not mentioned at Deprecated features - OpenStreetMap Wiki.